A new algorithm for simulation of chemical equilibria is developed, based on classical Newton-Raphson method applied to mass balance. This tool, named EST (Equilibrium Speciation Tool), is improved by using a robust Genetic Algorithm. In addition, EST works by using Excel spreadsheets and therefore offers the innovation of a great simplicity and versatility. In fact, it allows the users to simulate, or to obtain from experimental data, desired chemical-physical parameters as well as to interact with other available or freely created Excel tools. The reliability of this utility is here proved by comparison with some published data by other authors, concerning both complicated homogeneous and heterogeneous equilibria. In addiction its flexibility is tested computing thermodynamic parameters by using experimental calorimetric data referred to the complex formation of cobalt(II) with a macrocyclic ligand. A brief review and comparison of the relative robustness and quickness of main numerical methods are also reported.

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The formation of Co II complexes with differently methylated N-donor ligands ethylenediamine (en), N,NЈ-dimethylethylenediamine (dmen), N,N,NЈ-trimethylethylenediamine (trmen), and N,N,NЈ,NЈ-tetramethylethylenediamine (tmen), has been studied at 298 K in both the aprotic solvent dimethyl sulfoxide (dmso) and in an ionic medium set to 0.1 mol dm −3 with Et 4 NClO 4 under anaerobic conditions. UV/Vis spectrophotometric and calorimetric measurements were carried out to obtain the thermodynamic parameters for the systems investigated. Only mononuclear CoL j 2+ complexes were formed (j = 1−3 for en, j = 1, 2 for dmen; and j = 1 for trmen and tmen) where the diamines act as bidentate agents.

CdII and CoII complex formation with pyridine (py), 2,2′‐bipyridine (bipy), 2,2′6′,2″‐terpyridine (terpy), 2‐(aminomethyl)pyridine (amp), and bis[(2‐pyridyl)methyl]amine (dpma) was studied at 298 K in the aprotic solvent dimethyl sulfoxide (DMSO) and in an ionic medium set to 0.1 mol dm–3 with Et4NClO4 in anaerobic conditions. Potentiometric, UV/Vis spectrophotometric, and calorimetric measurements were carried out to obtain the thermodynamic parameters of the systems investigated. Enthalpy‐stabilized mononuclear MLj complexes are formed, whereas entropy changes counteract complex formation. These results are discussed in terms of different basicities, steric requirements, and solvation, of both the ligands and the resulting complexes. Density functional theory (DFT) calculations were carried out in order to obtain structural information and binding energies in vacuo. The DFT results are correlated with the solution studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The kinetics of the oxygenation reaction of CoL2(2+) complexes (L=ethylenediamine (en), N,N'-dimethylethylenediamnine (dmen)) have been investigated in dimethyl sulfoxide (dmso) at 298 K and in a medium adjusted to 0.1 mol dm(-3) with Et4NClO4 by means of a UV-vis spectrophotometric technique. The reaction mechanisms are consistent with the fast formation of superoxo 1:1 initial CoL2-O2 species (L=en, dmen), whereas the dimeric mu-peroxo (CoL2)2O2 adduct is formed only when L=en, in the rate determining step. The kinetic results are discussed taking into account the effects of ligand/solvent substitution. EPR results give information on the electronic structure and the coordination geometry of the Co(II) complexes and further confirm the stoichiometry of the species formed. Ab initio calculations provide insights on the geometrical parameters of all the complexes investigated and allow us to draw some hypotheses about the influence of H.H nonbonded interactions in the eventual formation of the dimeric mu-peroxo (CoL2)2O2 complexes. Solvational effects are also considered. The formation of the (CoL3)2O2 adduct is also proved when L=en by means of O2 volumetric absorption.